Air compressor



H. s. BRooM 2,936,949

AIR COMPRESSOR 5 Sheets-Sheet 1 May 17, 1960 Filed May ze, 1954 H. 5. BROOM AIR COMPRESSOR May 17, 1960 Filed May 25, 1954 5 Sheets-Sheet 2 /N VEN Tak H. S* BR 00M MMM mu@ May 17, 1960 H. s. BROM 2,936,949

AIR COMPRESSOR Filed May 26, 1954 5 Sheets-Sheet 3 L` O l o O a3 l E9?) O O O o o jo /NvfNTR H. 5. BRDQM May 17, 1960 H. s. BRooM 2,936,949

AIR COMPRESSOR Filed May 26, 1954 5 Sheets-Sheet 4 May 17, 1960 H. s. BRooM 2,936,949

AIR COMPRESSOR Filed May 26, 1954 5 ASheets-Sheet 5 27,936,949 Y coMPREssoR Harry Skeet Broom, High Wycombe, England, assig'nor to Broom.& Wade Limited, High Wycombe, England, a British company Application May 26, 1954, Serial No. 432,569 claims priority, application eretti Biiein May-zs,1953 ciaimsr. (ci. 23o-152) This invention comprises improvements in orrelating to air compressors.r

It is an object of the invention to provide an improved air compressor of the type in which a varied rotor "1s employed to compress the airand in which cooling is effected by oil particles suspended inthe air so as to be carried through the compressor with the air flow and'subsequently separated from the air under pressure and returned to the compressor for re-use. In a compressor of this type no .water jacket is ordinarily` required but when air is to be compressed to a` :pressure of the order ofone hundred pounds per square inch or more it is usually necessary to effect the compression in more tha'n one stage. It is an'object of the present invention to so design the compressor that the tendency which exists in apparatus of this type to throw the oil out of suspension in the air and allow it to collect'in inter-chambers and the like, is obviated or minimised.

According to one feature of the present invention in a compound compressor ofthe type referred to, a low pressure rotor is locatd'parallel with and close to a higher pressure rotor and the deliveryof thelower pressure rotor is arranged peripherally and immediately adjcent to a peripheral intake to the higher pressure rotor so thatjthe so that the air carrying the oil ydescends directly from one rotor to the other. In another construction, the two rotors are arranged side by side. Preferably, the rotors revolve in opposite directions and the point of contact of the lower pressure rotor! with its casing is to one side of the plane containing the axes of the rotors, while the point of contact of the higher pressure rotor is to the other side of said plane,`so that the path` of"the air through the rotors follows a curve free of any sudden change of direction which might tend to throw oilout. of suspension by local shock or turbulence or centrifugal effect.v f

Preferably oil is injected into the casings which containthe vaned rotors by inlets to each rotor located more or less tangentially to the periphery of the casings at a point close to that where the volume enclosed between adjacent vanes commences to contract.

'Ihe following is a description by way of example of certain constructions in accordance with theY invention:

In the accompanying drawings, Figure 1' is a vertical longitudinal section through one construction,

Figure l2 is a cross-section upon'the line 2-7-2 of Figre 1 looking in the direction of the arrows,

nted States a'fo i receive the engine flywheel (not shown).

93ans Patented May 17, 1960 ICG , ;2 Y Figure 3 is a d etail of an oil pump in section upon the line 3;-3 of Figure 1, looking in the direction of the arrows, and e' Figure 4 is a section upon the line 44, Figure 5 is a cross-section of a second construction, Figure 6 is a longitudinal section upon the line 7'7 ofFigure 5, looking in the direction of the arrows,

Figure 7 is a similar section'upon' the line 8-8 of Figure 5; f

`The compressor about tol-be described is intended to be bolted on to the end of the crank case of an internal combustion engine whichidrivesl it and the rst part of Vthe compressor consists of a casting 11 which forms a bell-housing on the end of the crank case and supports a rotor casing 12. The bell-housing is large enough to To the centre of the ywheel is bolted a sleeve 13 formed with internal driving teeth. The flywheel space is shut off from the rest ofthe interior of the bell-housing by a partition 14 which is cast integral With the housing 11 and the sleeve 13 projects through an aperture in the partition, 'which is sealed by an oilseal 15 bearing on the exterior of the sleeve. Within the partition the rotor casing 12 has an end-plate 16 bolted to it,'andv on the end-plate in line with the flywheel, is arjournal roller-bearing 17 for a rotor-shaft 18, The rotor-shaft 18 extends' from its roller bearing'towards the flywheel and keyed to it is a spur gear 19 having a'hub 20 which extends into the internally toothed sleeve 13 and carries external teeth to enter the teeth in the sleeve and thus to be driven thereby. Above the rotor-shaft 18, in the end-plate 16, is another roller bearing 21 for a second rotor-shaft 22, which carries a spur gear 23 meshing with the spurV gear 1-9 on the rst rotor-shaft and of the same diameter, so thatthe -two shafts are driven at the same speed but in opposite directions. z Y v The rotor casing (or stator?) 12 has a flange 24which is-bolted to the bell-housingA 11, fand itcontains two 'cylindrical bores 25,'26 (Figure 2) whichy are eccentric to the axes of the rotor-shafts 18, 22 respectively. The outer end ofthe stator beyond the cylindrical bores is faced to receive cover plates 27, 28 (Figure 1) one for eachfbore. The two cover plates contain journal bearings 29, 30 for the outer ends of the rotorshafts. Inside each of the bores 25, 26 in the stator is a rotor (31 for the shaft 18 and 32 for the shaft 22) each of which is formed in one piece with the rotor-shaft to which it bef longs. The rotors 'are eccentric to the bores in which they workand areV of such diameter as to t close to them at one side asis shown in Figure 2. Each rotor is slotted longitudinally from end to end to receive eight sliding -vanes (marked 33 for the rotor 31 and 34 for rotor `32).

The upper rotor 32 is somewhat longer than the lower one and is of larger diameter and constitutes -a -low pressure stage. Above the upper rotor is an inlet chamber 35 with a large port 36 in the top face ofrotor casing above which is mounted an unloading valve 37, shown only in Figure 1. The upper cylindrical bore 26 in the stator has in its upper side where it lies below the inlet chamber three wide slots 37, 38, 39 which extend part of the way around its periphery and permit access of air to the upper-rotor.V On its under side there are two delivery slots 40, 41 which open into an inter- The bore of the stator which contains the lower rotor has inlet slots 43, 44 immediately below thev delivery slots 40,` 41v from the upper-'rotor and ithas delivery ports 45, 46 which open outof the side of the stator approximately on the same level as the axis of the lower rotor.

The upper rotorLas viewed endwise has its axis displaced to one side of the bore in whichity works and a' little below the level of the centre of the bore, so that itY Y @essere almost touches the interior of the cylindrical bore along the side between the inlet port 38 and outlet port 41 of the bore. The lower rotor is eccentric to its bore, which it approaches at one side of and above the centre of the bore, towards the opposite side ofthe stator vfrom that which is approached by the; upper rotor, thek position Vof nearest approach being located between the inlet port 43 and delivery port 45 of; the lower rotor. As'r the rotors are geared together they move in opposite directions and the direction of rotation in such that each of them moves its vanes across the inlet in a direction away from the place at which the rotor approaches the bore, and then with the vanes sweeps the air down through the underside of the bore and the delivery port. The position at which the lower rotor approaches the bore is nearer to the top of the boreV than in the case of the upper Vrotor in order that the delivery ports 45, 46 may be at one side of the rotor instead of below it. The effect of this arrangement is that air moves downwards into the upper rotor, is carried in a curved path around the .upper rotor 32 and given aiirst stage of compression, coming out of the bottom of the rotor and moving across the interior of the interchamber 42, without any substantial kchange of direction, to the inlet of the lower rotor. It comes on to the vanes ofthe lower rotor while moving in the same direction as these vanes and is swept around by them to the outlet 45, V46. This gives` the air a path shaped somewhat like an elongated letter S and avoids turbulence or sudden change ofdirection of movement.

There is an oil inlet 47 to the upper rotor which sprays oil into the same at a point approximately coinciding with maximum distance of the rotor from the casing wall, that is to say at the place where the air is at its least pressure. Oil sprayed in at this position becomes suspended in the air. Owing to the smooth path of the air and to its downward movement there is little or no tendency to precipitate oil droplets out of the air and thewhole of the oil with the air is carried around to the delivery port. Moreover by this means the oil pressure required is much less than the maximum air pressure. There is an oil inlet 48 to the lower rotor.

On the back of the cover plate 28 of the lower rotorshaft there is bolted a casing 50 (Figure l) for a gear pump for oil. This comprises an upper gear 51 which is driven by a splined connection 52 with the lower rotor shaft and a lower gear 53 which is driven by meshing with the first. On the Apair of spindles 54.55V which supports the two said gears there are two additional pairs 56, 57 and 58, 5,9V of narrower gears. The casing 50 has an inlet 60 and a delivery port 61. Between Athe inlet and the delivery port isa relief valve 62 (Figure 3). The gears 56, 57 work in a casing 63 having an inlet 64 and a delivery port 65. This is separated by a diaphragm 66 from the casing 50. The gears 58, 59 work in a casing 67 which is separated by a diaphragm 68 from the casing 63 and outside the casing 67 is a cover plate 69. All these parts are drawn together by bolts 70. v

The larger pair of gears 51, 53 is used to deliver oil at low pressure to the spray point 47 in the bore of the stator 32. The smaller gears collect oil filtered from delivery-air and return it to the system.

The smaller pair of gears 56, 57 is used to deliver oil at a higher pressure to a spray point 48. The pair of gears 58, 59 delivers oil to the journal bearings 17, 21, 29 and 30. The rear faces of the vanes 33, 34 are slotted as shown at 71, 72 to help to carry oil down to the spaces beneath them and to ensure that air pressure,

behind the vanes is. equal to that in the space in which the vanes work against the casing.v This'permits the vanes to move outwardly freely under the effects of centrifugal force when the apparatus is in motion.

Appropriate pressure seals are located at the various joints.

Above the air inlet to the rotor casing is an unloading valve 74. This takes the form of a Vdouble-beat valve and 59 of Figure l.

urged by a light spring 75 in one direction to close it but opened by the air flow. It is closed under the effectsv of a piston 76 which is subjected to the delivery pressure. At the delivery of the pump there is placed a light spring-pressed disc-valve 77 which serves to hold up airv Vpressure in the receiver'when the pump is unloaded.

Referring now to Figures V5 to 7, the general relative disposition of the parts is similar tov what has already been described, with two rotors arranged parallel to one another, but in this case, the two rotors are in the same horizontal plane. Two cylindrical boresk 80, 81 are arranged side by side in a casing 82, and contain two eccentric rotors 83, 84 having vvanes 85, 86. There is an inlet unloading valve 87 similar to the Yvalve Y37 already described, and from this the air descends through a port 88 into the upper part ofthe casing 82- and enters the larger or low pressure cylinder by way of ports 89. Oilis injected into this cylinder through a nozzle 90 from a pipe 91, and the oil-laden air passes outA through ports 92 into an inter-chamber93 in the bottom of the casing 82 and thence upwardly through ports 94 into the highpressure cylinder 81.` Here there is a further oil injection nozzle 95 and the air passes out through ports 96 andpast a delivery valve 97, which latter corresponds to the valve 77 of Figure 2. The path of the air through this apparatus instead of being shaped like the letter S, as in Figure 2, is more like the letter G but here again as much care as possible is taken to avoid undue or sudden changes of direction.

Ascan be seen from the longitudinal sections, Figures v6` and 7, the low-pressure rotor 83 forms part of a forging which comprises a driving shaft 98, splines 99 and working-in roller bearings 100, 101. The casing 82 is closed on the driving side, by'an end-plate 102, and the bearing 100 is mounted in the end plate. A space outside the end-plate is enclosed by a gear case 103, and within the gear vcase is a spur gear 104 keyed to the shaft 98. The gear case carries brackets 105 which support a ange 106 for connection to the flywheel `casing of an internal combustionV engine which drivesthe compressor.

The spur gear 104 meshes with a second spur gear 107 in the casing 103, the gear 107 being mounted on a shaft 108 whichis integral with the highpressure rotork 84.

On the casing 82 at the opposite end fronrthel endplate 102, is a cover 110, andthe part of the cover 1 ,10` which encloses the rotor 84 has secured to it pump casings 111, 112, 113 and an outer pump, cover` 114. pump casings 111, 112 and 113 there operate pump gears 114, 115,116 which correspond .to the gears 51, 56, 58 of Figure l. These mesh respectively with gears 117, 118 and119 which correspond to the gears 52, 57 The three gear pumps are connected respectively to the low-pressure nozzle 90, to the highpressure nozzle 95 and to the bearings of the rotors in a similar way to the corresponding connections of Figures v lt is to be understood that if necessary in either of the constructions'described, one of the higher pressure gear pumps might be dispensed with and the bearingsfed from the same pump as that which supplies the high-pressure rotor cooling nozzle 48 or 95 as the case may be.

Although in the specific embodiment described the de-4 sign is shown as being suitable for direct drive from an internal combustion engine, it is to be understood that any desired form of drive could be adopted such, for example, as a direct drive from an electric motor, or any other normal form of prime mover, or a belt drive or the like.

I claim:

l. In a compound compressor, a casing having a low pressure rotor chamber, and beside it a high pressure rotor chamber, a low presure rotor eccentrically disposed in the low pressure chamber and carrying sliding vanes which divide the chamber into spaces which expand and contract upon rotation of the rotor, a high pressure rotor eccentrically disposed inthe high pressure. chamber In the Y assenso' y and likewise having sliding vanes, said rotors their chambers being located parallel and close to one another, means for dispersing oil in the air passing through the low pressure chamber, said low pressure chamber having lateral delivery ports, said high pressure chamber having lateral' intake ports, said delivery and intake ports being substantially in alignment in a direction transverse to the axes of the rotors and in direct unimpeded communication with one another yfree of interposed obstacles so that the air carrying the oil passes directly from the low to the highpressure rotor chamber without impinging on any surface which would baliie its flow, and driving means to drive said rotors at appropriate relative speeds to cause the Alow pressure rotor vanes to sweep out a greater displacement than the high pressure rotor vanes.

. 2. A compound compressor as claimed in claim 1 wherein the rotors revolve in opposite directions, and the point of contact of the low pressure rotor with its chamber is to one side of the plane containing the axes of the rotors, while the point vof contact of the high pressure rotor is to the other side of said plane, so that the path of the air through the rotors follows acurve free of any sudden change of direction which might tend to throw oil out of suspension by local shock or turbulence or centrifugal force. i

3. A compound compressor as claimed in claim 1 wherein the means provided to disperse oil into the air comprises inlets located substantially tangentially to the 5. A compound compressor comprising in combnation a casing having high and low pressure rotor chambers extending parallel with one another and close together, rotors eccentrically disposed in each chamber each carrying sliding varies to divide the chambers into compartments, means for dispersing oil in air entering the low pressure chamber, said low and high pressure chambers having intake and delivery ports, said delivery ports of the low pressure chamber and intake ports of the high' pressure chamber being substantially in alignment with each other in the direction of ow of air from the delivery to the intake ports and said casing providing a passage from the said delivery to the said intake ports free of interposed obstacles, so that the air carrying the oil passes directly from the low to the high pressure rotor chamber without impinging on any surface which would baille its flow, and means for driving the low and high pressure rotors at appropriate relative speeds.

References Cited in the le of this patent UNITED- STATES PATENTS 936,932 Neumann -a Oct. 10, 1909 1,476,482 Berrenberg Dec. 4, 1923 1,531,607 Green Mar. 31, 1925 1,895,816 fPfeiier Jan. 31, 1933 2,062,045 Van Deventer Nov. 24, 1936 2,126,247 xEppers Aug. 9, 1938 2,150,122 Kollberg et al. Mar. 7, 1939 2,185,338 Hassler Jan. 2, 1940 2,309,443 Cuthbert Jan. 26, 1943 2,641,405 Valley June 9, 1953 2,668,655 Bowering Feb. 9, 1954 2,691,482 Ungar Oct. 12, 1954 2,780,406 Feldbush- Feb. 5, 1.957

FOREIGN PATENTS 444,995 Italy n Feb. 3, 1949 506,341 Great Britain May 23, 1939 kGreat Britain May 6. 

